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Monday, September 20, 2010

GLD TV FIELD COLLAPSE WITH A SINGLE HORIZOTAL LINE across the picture (clear picture below the line but distorted picture above the line. Also white lines across the upper part of the screen. There is also blank part above and below the screen.

In my opinion a technician and a medical doctor have a lot in common, we deal with symptoms(facts) analyze them and figure out from the data at hand the most likely cause of those symptoms.

Fortunately for doctors they have added advantage because at least with human being they can speak out how they are feeling, add some additional test and there you go, Drug prescription is done. Ok?

Now for technician’s machines don’t speak, therefore we rely heavily on keen observations, testing critical test point, some history from the owner on how the problem started etc to be able to figure out the actual circuit causing the problem (symptoms) at hand.

This part is very critical, the more information you gather the more likely you are going to narrow down to the actual circuit which is causing the problem.

If the machine (Television or Monitor) has something on the screen, you can get a lot of clues on the screen behavior even before opening the machine.

Let take this GLD TV as a case study, the information on the headline of the article is what I was able to observe on the screen.

I have tried to reproduce the symptoms on the picture below

1. Screen height is narrow.

2. A SINGLE HORIZOTAL LINE across the picture

3. Clear picture below the line but distorted picture above the line.

4. Also lines across the upper part of the screen.

5. There is also blank part above and below the screen.

These are 5 strong facts all pointing to Vertical Circuit, am I right?

NOW LET OPEN THE TELEVISION AND TEST OUR ANALYSIS

After opening this particular set I noticed two capacitors 1000uf/35v which had their top silver part swollen. I put my finger on them and they were also getting hot. This was enough evidence that these two capacitors are faulty.

Both capacitors were on the secondary output source and after following that source it lead me to the vertical IC (LA78040). Even if this capacitor were not swollen I would have gotten them pretty easily because the first thing I could have done is testing the supply to the vertical I.C. If capacitors with filter functions develop problems (fail) usually causes the voltage to drop on that line. If the voltage is lower than normal there will be subsequent effects on that circuit may it be vertical, RGB, horizontal etc.

I replaced the two capacitors plus the vertical I.C to avoid call back because I figured out that because this IC was being feed with dirty dc (not clean dc) it might have developed some internal injury which might manifest after sometimes.

ConclusionWhenever you see a single horizontal line across the screen always suspect problem on the vertical circuit regardless of other symptoms on the screen. Usually vertical problems manifest themselves in various ways with some being weird (funny). Also presence of lines on this circuit besides the single lines is a strong indication that a capacitor might have failed too on that circuit. I.e. vertical

After you have localized the faulty circuit open the set and go straight to the suspected Circuit. In this case vertical circuit was suspect. Do a thorough scan on all components around the vertical I.C. usually symptoms like lines on the top of the screen and sometimes a black stripe or no image at the bottom are pointer that one or more capacitors are faulty. Scan and check any bulging capacitor top or capacitor getting hot which are sighs of bad capacitor.